Long Distance Transportation Patterns: Mode Choice

Americans total 1.3 trillion person-miles of long distance travel a year on about 2.6 billion long-distance trips. Long-distance trips are journeys of more than 50 miles from home to the furthest destination. More than half of long-distance trips are taken for pleasure, while fewer than one out of five long-distance trips is for business. While most long-distance trips are made by personal vehicle, the National Household Travel Survey (NHTS), conducted in 2001 and 2002, explored the choices that travelers make for their long-distance travel.

Among the key findings are:

• Long-distance trips originating in urban and metropolitan areas are more likely to use public transportation modes than trips originating in rural and non-metro areas.
• About 8 percent of long-distance trips that use a public transportation mode^[1] use a different mode in each direction of travel.
• Almost 90 percent of long-distance trips are by personal vehicle.
• Mode choice varies somewhat by trip purpose and distance.
• Personal vehicle is the most frequent mode used to initially access long distance public transportation, but on the arrival end a greater mix of modes is used.

A more detailed discussion of these findings follows.

Long Distance Travel Mode

Based on the 2001–2002 NHTS data, Americans take 2.6 billion long-distance trips per year, or 7.2 million trips per day. Almost 9 out of 10 long-distance trips are taken by personal vehicle,^[2] and about 10 percent use public transportation modes. Over 7 percent of long-distance trips are taken by air, while 2 percent are by bus (including scheduled, charter, and other bus trips). Train travel represents almost 1 percent of long-distance trips. Table 1 in the Appendix shows the breakdown by mode.

Mode by Trip Purpose

More than half of long-distance trips (56 percent) are taken for pleasure, 16 percent for business, 13 percent each for commuting and for personal business,^[3] and 3 percent for other reasons. Regardless of trip purpose, driving is the primary travel mode, accounting for 89 percent of all trips. Contrary to the popular vision of business travelers flying off to their meetings, nearly 80 percent of all business trips are done by driving. Personal vehicle travel accounts for 96 percent of commuting trips and about 90 percent of pleasure and personal business trips. Air travel accounts for only 18 percent of business trips, overall. About 7 percent of pleasure trips are by plane, and air accounts for only about 5 percent of personal business trips. Rail travel accounts for about 2 percent of all business trips and commute trips, but less than 1 percent of pleasure trips.

While personal vehicle and air are the primary and secondary modes for all other trip categories, bus is as important as air as the secondary mode for personal business trips.^[4] Table 2 in the Appendix shows the modal breakdown of long-distance trips by trip purpose. Figure 1 (and table 3 in the Appendix) shows the modal breakdown by purpose for trips made by public transportation modes (personal vehicle trips excluded).

Mode by Trip Distance

Mode choice changes with trip distance. Trips of 50 to 499 miles, each way, account for 90 percent of long-distance trips. About 5 percent of long-distance trips are to destinations 500 to 999 miles away, and another 5 percent are 1,000 miles or longer. At shorter distances most trips are by personal vehicle, but the percentage of trips taken by public transportation increases with trip distance. For trips of less than 250 miles, 97 percent of trips are by personal vehicle, but once the trip distance is 750 miles or greater, travelers are more likely to use one of the public transportation modes.

At distances of 1,500 miles or more, only 15 percent of trips are by driving, with the large majority of trips (82 percent) being by air. Figure 2 shows how as trip distances increase, personal vehicle is replaced by air as the primary transportation mode. Because the share of trips using any of the other public transportation modes (bus, rail, and “other”) never exceeds 3.3 percent, and in many cases the sample is too small to be reliable, they are not shown on figure 2. Table 4 in the Appendix gives detailed information for all modes.

Mode Choice for International Trips

It is not surprising that U.S. residents’ choice between the two primary modes (air and personal vehicle) is much different for international trips than it is for domestic trips.  Slightly more than half of international trips are by air, compared to only about 7 percent of domestic trips. Virtually all international trips to destinations outside of North America are by air. Within North America, about 86 percent of Caribbean trips are by air, and 29 percent of trips to both Canada and Mexico are by plane.

Personal vehicle, which accounts for over 90 percent of domestic trips, still accounts for 42 percent of international trips due to the volume of driving trips to Mexico and Canada. Those two countries account for 65 percent of international trips; driving accounts for about two-thirds of the trips to both of those countries.

Appendix table 5 compares mode choice for international and domestic trips. Table 6 shows mode choice for international trips by various destination areas of the world. The sample size for bus, train, and other modes is too small to be reliable.

Trips Using Different Modes in Opposite Directions

Not all travelers use the same mode for their going and return trips. About 8 percent of long-distance trips that involve travel on one of the public transportation modes will be made using a different transportation mode in the opposite direction. Among public transportation users, air and bus travelers are least likely to use a combination of modes, with only about 6 percent of air travelers and 10 percent of bus travelers using a second mode in the opposite direction.^[5] About 17 percent of rail trips use a different mode in the other direction, although there is not a statistically significant difference between the percentage of bus, train, or “other” ^[6] trips that are likely to use a different mode in each direction. The sample size in the NHTS for the “other” modes is not large enough to provide a reliable estimate. Personal vehicle is the second mode of transportation for 79 percent of the multiple-mode long distance public transportation trips. Twenty-one percent of multiple-mode public transportation trips use another public mode in the opposite travel ­direction.

Because personal vehicles are used for 90 percent of all long-distance trips, multiple-mode trips represent a considerably lower percentage of personal vehicle trips than for the public transportation modes. Less than 1 percent of long distance personal vehicle trips use a different mode in the opposite travel direction.

Table 7 of the Appendix shows for each mode the percentage of trips that use the same mode and the percentage of trips that use a different mode in the opposite directions. Table 8 shows the percent of trips in the opposite direction that are via personal vehicle, for trips that use a public transportation mode in at least one direction. Table 9 shows the detail of return mode usage by going mode for all trips.

Mode Choice by Geography

There is a difference in intercity travel mode choice depending on where the traveler resides. While all groups rely predominantly on personal vehicles, those who live in urban areas are more likely than those who live in rural areas to use public transportation for their long-distance trips.

While the personal vehicle is the predominant mode for all travelers, those who live in rural areas use it for 95 percent of long-distance trips, while the personal vehicle is used for only 87 percent of trips originating in urban areas. Nine percent of long-distance trips originating in urban areas are made by air compared to only 3 percent by air from rural areas. Similarly, 1 percent use rail from urban areas, compared to about one-half of 1 percent in rural areas. There is no statistically significant difference between the use of bus in rural or urban areas, with about 2 percent of trips from both rural and urban households using that mode. Table 10 shows the urban/rural breakdown by mode.

Mode choice varies even between metropolitan areas of different size. Those living in Metropolitan Statistical Areas (MSAs) of 1 million or more population are more likely to use public transportation modes for long-distance trips than those who live in smaller metro areas. Those living in the smaller metro areas in turn use public transportation for a higher percentage of long-distance trips than those living outside of metropolitan areas. For example, in MSAs of more than 1 million residents, 85 percent of long-distance trips are made by driving and 15 percent are made using public transportation. In MSAs of less than 1 million, the percent of trips made by personal vehicle increases to 92 percent with the percent made by public modes dropping to 8 percent. Outside of metro areas, 96 percent of long-distance trips are made by personal vehicle, with only 4 percent using public modes. See table 11 in the Appendix for a breakdown of personal vehicle and public transportation long-distance trips by the MSA size.

Demographics and Mode Choice

Across all age groups, the personal vehicle accounts for about 90 percent of long-distance trips. The remaining 10 percent of long-distance trips are made via public transportation modes. Air service is the most frequently used public mode for long-distance trips by all age groups except those age 65 and above.

Among that age group there is no statistical difference between the percentage of trips made by air and the percentage made by bus.

Mode choice by age group is shown in Appendix table 12.

While driving is the dominant mode across all income levels, household income has an influence, especially at the upper and lower levels, on mode choice. While personal vehicle is the dominant mode for all long-distance travel, the percentage of trips made by driving declines noticeably for those with incomes over $75,000 annually. Below that income level, more than 91 percent of long-distance trips are made by driving, but that figure drops to 84 percent for those in the highest income group. At the same time, those with incomes in excess of $75,000 make nearly 14 percent of their long-distance trips by air, compared to only three to 5 percent of trips by those below that income level.

Those with household incomes below $25,000, on the other hand, are more likely to make trips by bus than those at the higher income levels. Almost 4 percent of long-distance trips are made by bus among those making less than $25,000; but that share declines to less than 2 percent for those in the highest income bracket. There is no difference across income levels in the percentage of long-distance trips made by train. 

Income breakdown by mode for long-distance trips is shown in Appendix table 13.

Access and Egress Modes

Auto travel is generally door-to-door. However, those using public transportation modes for long-distance trips must get from the starting point to the intercity transportation terminal to board the public transportation mode. Similarly, at the destination, public transportation travelers need to get from the intercity transportation terminal to their actual destination location. The trips to access and egress the main transportation mode are examined in this section of the report.

The most frequent access mode used at the originating end of the trip is the personal vehicle, accounting for 71 percent of trips to access public long-distance transportation. Three out of four air trips begin by either driving or being driven to the airport, while 66 and 54 percent of bus and train trips, respectively, begin with access being provided by personal vehicle.

Public transportation is used by 15 percent of those needing to access a long-distance transportation terminal, and 10 percent use a combination of more than one mode to get from their origin point to the terminal. Overall, about 3 percent walk or bike to the terminal. However, bicycle and pedestrian access is used to access nearly 13 percent of long-distance train trips and over 10 percent of long-distance bus trips. Appendix table 14 shows how travelers access intercity transportation.

The significant use of local public transportation to access intercity modes (non-personal vehicle) is a phenomenon of the large metropolitan areas. In MSAs of more than 1 million population, where there are generally extensive public transit networks, about 18 percent of those accessing an airport, bus, or rail station use public transportation. This compares to less than 10 percent access by public transportation in MSAs of less than 1 million population, and non-MSA areas. Table 15 shows the access mode by MSA size.

At the arrival end of the trip, travelers use a greater mix of modes to egress from the intercity terminal to the final destination than they use for access. Personal vehicle is the primary egress mode only for those arriving by air. About two-thirds of arriving air travelers leave the airport via personal vehicle. Personal vehicle includes rental cars. Personal vehicle does not include taxicabs, which are counted in the “other” mode category. About one-fourth of air passengers use local public transport to egress from the destination terminal. Rail passengers are just as likely to get to their destination by walking, using local transport, using a personal vehicle, or taking a combination of more than one egress mode. Intercity bus travelers are most likely to walk or bike to their destination (44 percent) or use public transportation (33 percent). Table 16 shows how long-distance travelers get from their arrival terminal to their final destination.

While the access mode seems to be influenced by MSA size on the originating end of the trip, the arrival MSA size does not seem to have as great of an influence on egress mode. Regardless of MSA size, about half of trips are completed in personal vehicles, about one-fourth by public transit, 10 to 15 percent by walking or cycling, and about 10 percent by a combination of two or more modes. Table 17 shows egress modes by MSA size.

Methodology Notes

This analysis is based on the “national sample” long-distance trip file of the National Household Travel Survey. Long-distance trips are defined as those where the destination is at least 50 miles away from the originating point.

The modal analyses in this report use only trips where transportation mode information is available. Trip records are not considered if mode choice is “unknown” or if mode choice was not provided by a survey respondent. Less than one-half of 1 percent of the 2.6 billion weighted long-distance trips were eliminated due to the lack of mode information.

Public Transportation refers to all modes except Personal Vehicle. Public Transportation modes are air, bus (both scheduled and charter), rail, and other (primarily ship, limousine, taxi, shuttle services, bicycling, walking). In the analysis of modes used to access long distance transportation modes, bicycling and walking (bike/walk) are considered separately.

The NHTS data were collected from March 2001 through May 2002. The September 11, 2001 attacks on New York and Washington had an impact on travel, especially travel by air, in the following months. BTS is analyzing the impact of the 9/11 attacks on travel in the United States, but that analysis has not yet been completed, and thus the impact of those events cannot yet be quantified for the NHTS data used in this report. While those attacks likely had some impact on travelers’ modal choice and the percentages using the various modes, we do not believe at this time that the impact was significant enough to change the basic findings in this report.

Comparisons made in this report are statistically significant at a 0.05 level.

Appendix

The following tables provide the data on which this report is based. The percentages used in each table are weighted, and standard errors are provided for all data in the tables. Cells with a small sample size (less than 30 observations), or with a coefficient of variation greater than 0.3, which can make the estimates unreliable, are shown underlined. Note that in many cases the sample size for other, train, and bus are too small to be reliable. Cells that are not statistically different from others in the same row are shaded. Notes below the tables clarify the statistical significance shading or other information where necessary.

End Notes

^[1] Public transportation refers to all transportation modes except personal vehicle.

^[2] Personal vehicle includes car, van, noncommercial truck, recreational vehicle, sport utility vehicle or motorcycle.

^[3] Personal business trips are those taken for family, personal, religious or medical reasons.

^[4] The percentage of personal business trips completed by bus (5.6%) and air (4.7%) are not statistically different.

^[5] There is no statistical difference between the percentage of air and bus travelers using a second mode.

^[6] Examples of “other” modes are ship, ferries and limousines.